Improvement And Application Of The Near-field Scanning Optical Microscope

The thesis mainly focuses on the improvement and application of the digital mode near-field scanning optical microscope (NSOM), which is originated as an analog mode NSOM by former researchers. The control mode of the nano-positioning flat is changed from analog to digital. Substituting the photomultiplier (PMT), a single-photon counting avalanche photo-diode (APD) is used as the light collector. The author researched on different near-field detectors based on the shear force mode NSOM and modified the near-field distance control and scanning programs. Various nanostructures were investigated by the newly developed digital mode NSOM.The fiber probe with the tip diameter of about 100nm is fabricated by the chemical etching technique. Using the electrochemical deposition method, we have successfully fabricated a sub-probe with the tip diameter of about 100nm on the coated fiber probe tip (with tip diameter more than 1μm). It is suitable for tunneling current exciting as well as for near-field detection. Different near-field detectors, such as piezoelectric bimorph cantilever, piezoelectric bimorph cantilever-single tine oscillating tuning fork and piezoelectric bimorph cantilever-double tines overtone oscillating tuning fork near-field detectors, are employed to control the near-field distance. Utilizing the piezoelectric bimorph cantilever-double tines overtone oscillating tuning fork near-field detector, the scan speed is greatly fastened for the samples with large height differences. The scan precision and the localization precision are greatly improved in the digital mode of the nano-positioning flat and in the shear force distance control mode of the piezoelectric bimorph cantilever-single tine oscillating tuning fork near-field detector. Assorting to the digital mode NSOM, near-field distance control and scanning programs were amended. The author also wrote the tunneling current distance control and scanning programs, which are assorted to the tunneling current exciting fiber probe. Using the programs, one can fabricate ordered metal nanostructures on fast ionic conductor (FIC) thin film surface.Employing the digital mode NSOM, shear force topographical and transmission optical images of the standard samples have been successfully taken. The system sensitivity of the topographical and optical imaging is proofed. The scan speed of the piezoelectric bimorph cantilever-double tines overtone oscillating tuning fork near-field detector is fastened by about 4 times for the sample of the cross section of the corn root. Based on research works on the incandescent emission of the carbon nanotubes (CNTs) bundles, the author also studied the incandescent radiation of the ordered CNTs bundle films under the alternative tunneling current exciting using the digital mode NSOM.